Segmental retaining wall blocks designed for curved or straight alignment

ABSTRACT

A segmented retaining wall block has one side wall that is rearwardly tapered so as to allow the block to turn a radius when placed in adjacent position with respect to another similar block. The block also has a rear wall provided with a protruding wing that projects laterally away from the tapered side wall. The rear wall is also provided with a bay that extends inwardly in the side wall that is opposite to the tapered side wall. The wing and bay have front edges designed as congruent arcs. The wing may be sized and shaped so as to protrude into the bay of an adjacent similar block to create a barrier when the adjacent blocks are in straight, convex or concave alignment for preventing infiltration of backfill material such as soil, into voids that exist between the backs of the blocks when installed.

INTRODUCTION

The present invention relates to segmental retaining wall blocks oftapered shape that are configured in such a manner as to preventinfiltration of backfill materials such as soil into voids that existbetween the backs of the blocks when installed.

BACKGROUND OF THE INVENTION

It is of common practice for a landscape architect, contractor orhomeowner, to design the layout of a proposed segmental retaining wall(SRW) in curved or snaking alignments. Curving alignments with tight orlarge radii, give a natural organic flow to the retaining wall that maybetter blend in with the natural environment when compared to straightlines and hard corners.

Currently, the segmental retaining wall blocks used to achieve curvedalignments have one or both of their sides that are tapered when theblocks are viewed in top plan view (i.e., the width of the rear of eachblock is less than the width of the face of the block).

In practise, some manufacturers offer standard blocks with front andrear of the same width for the manufacture of straight walls (see FIGS.1 a and 1 b identified as “prior art”). They also offer tapered blocksfor used to give curved sections to the walls (see FIGS. 2 a and 2 balso identified as “prior art”).

Alternatively, other manufacturers offer tapered blocks with rear wingsthat can be knocked off. Where the rear wings are kept, the blocks beused as such to build a straight wall (see FIGS. 3 a and 3 b identifiedas prior art). When the rear wings are knocked off, the constructor maythen create a tapered version of the block and used such blocks forcurved walls (see FIGS. 4 a and 4 b identified as “prior art”).

As may be appreciated, the taper or angle set into the sidewall(s) ofthe blocks dictate the minimum allowable convex radius the wall will beable to achieve. For a block that is tapered on both sides (dualtapered) or tapered on one side only, the same equation applies toresolve the minimum allowable radius the blocks can achieve when abuttedimmediately against one another in a curve or a circle. The equation isas follows (see FIG. 5).

D=Depth of Block (front to back depth)

Wf=Width of Face of Block

Wr=Width of Rear of Block

R=Minimum allowable radius of blocks

θt=Total Angle from vertical axis of block sidewalls

θt=(Tan⁻¹((Wf−Wr)/D)   (Equation 1)

$\begin{matrix}{R = \frac{\left( {180{Wf}} \right)}{\left( {{PI}\left( {\theta \; t} \right)} \right)}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

One major flaw exists with the current design of the tapered SRW block.Because the block is a “precast” unit, the taper is permanently set tothe “minimum” or smallest possible radius. This allows the user tocreate curves that have radii ranging from almost straight to thetightest possible radius. Although this does give the user flexibilityin creating both large and small radius curves, it also creates aproblem. When the tapered blocks are set at the highest possible radius,no gap exists at the rear of the wall (see FIG. 5 a identified as “priorart”). In other words, the rear wall formed at the back of the wall issolid, just like the face. However, when a radius is constructed that islarger than the minimum, which occurs most often, the total rotation ortaper of the block is not fully utilized. That is, a gap is left at theback of the blocks between each unit. If the radius is significantlylarger than the minimum, this gap can be considerable (see FIG. 5 bidentified as “prior art”). By experience, such a gapping in the back ofthe wall leads to the three following problems.

Problem 1—Backfill Material Migrate into “Voids” Creating Loss ofCompaction and Strength.

First, placement and compaction of backfill materials into these gaps isdifficult if not impossible and time consuming for the contractor. Inmany cases, this leads to backfill being placed loosely or not at all inthis “wedge” between the back of the blocks. Through the forces ofgravity and/or water flow, the backfill material adjacent to (behind)the back of the blocks may migrate into these voids over time, creatinga loss of compaction and soil density immediately behind the wall. Thecompaction of the backfill materials and subsequent soil density iscritical to the strength of the backfill materials and the performanceof the wall. As such, this mechanism may cause a loss of strength in thebackfill materials, which results in an increase in lateral earthpressure behind the wall, which is not generally accounted for instandard design practices. An increase in the lateral earth pressure, orforce, being applied to the wall reduces the overall factors of safetyassumed in design and may impact the structural performance of the wall.

Problem 2—Settlement of Backfill Materials Immediately Behind Wall.

Along with an increase in earth pressure, the movement of the backfillmaterials immediately adjacent to the back of the blocks results insettlement of the material in this zone. Settlement in the area(immediately behind the blocks) results in the following potentialproblems. First, settlement of backfill behind the wall may cause thegrade behind the wall to move downward, perhaps to an unacceptablelevel. Elements such as swales or asphalt paving constructed immediatelybehind the top of the wall may deform differentially, or totally, beyondwhat is allowable if settlement is excessive. Second, settlement bynature produces additional lateral earth pressures as the backfillmaterials are compressed both vertically and displace laterally. Third,when a geogrid reinforcement material is used to reinforce the backfillzone, settlement immediately behind the blocks may result in a failure.of the connection of the geogrid reinforcement to the block. As thebackfill material settles, the geogrid reinforcement, which is installedhorizontally, is subjected to a downward dragging force as it extendsout from between the blocks and into the backfill zone. This downwardforce created by the settling backfill materials, acts to drag thegeogrid down, over the back edge of the block. In some cases, the squareedge at the back of the block, combined with the presence of smallconcrete burs created at this seam during the manufacturing of theblock, are enough to damage or completely sever the geogrid, when it isbeing pulled down against it by the settling backfill materialsimmediately behind the block. This results in a lower or non-existentconnection to the block, at which point the structural integrity of thewall has been compromised.

Problem 3—Migration of Fine Materials Through the Face of the Wall.

Natural forces of gravity and water flow acting on the backfillmaterials may carry soil fines into these voids created by the gaps atthe back face of the wall. If these forces are sufficient, the soilfines may be carried through the voids and out to the face of the wall.The staining caused by the soil fines being deposited on the face of thewall is often unacceptable to the consumer from an aesthetic point ofview.

The problems listed above are the result of a tapered block being usedin applications where the radius being constructed is not the minimumradius. As such, gaps are created at the rear of the wall immediatelyadjacent to the backfill material. The backfill material is then notcontained and may migrate into these voids or gaps between the blocks,leading to the above issues.

SUMMARY OF THE INVENTION

The present invention relates to a segmental retaining wall (SRW) blockthat is unique in that it allows the user to construct inside andoutside (concave and convex) radii with the blocks, while maintaining afull barrier at the rear of the block to the infiltration of backfillsoils into the facing or through the facing.

Thanks to its particular configuration, the SRW block according to theinvention allows straight or curved alignments while directly addressingthe issue of the creation of large voids in the back of the wall thatoccurs with existing tapered SRW blocks that exist when the blocks arenot placed in the minimum convex alignment. The plan configuration ofthe SRW block according to the invention can be applied to any size ofblock, face shape or orientation. It provides lateral shear between theunits such as an integral tongue and groove, mechanical connectors orpins, adhesive, etc. Despite the method of vertically interlocking theunits (lateral shear between units), these elements would have to takeinto account the ability of the block to curve within certain limits.

More specifically, the SRW block according to the invention solves theabove mentioned problems encountered with prior art in that, thanks toits configuration, it blocks the migration of backfill materials at therear of the wall, regardless of the size of the radius or curvaturebeing constructed.

This SRW block is tapered to allow the block to turn a radius. Itcomprises a protruding wing or tab on one side, and the congruentreceiving “bay” area on the other.

When several of these blocks are placed adjacent to each other in astraight alignment, the wing protrudes or overlaps into the bay area acertain distance required to create a barrier against the migration offines when the block is placed in a concave alignment. The front edge ofthe wing and the front edge of the receptacle bay are designed ascongruent arcs, the front edge of the wing being set to a radius justslightly larger than the radius of the front edge of the bay area toallow for construction and manufacturing tolerance. As the blocks arerotated to achieve a curve, the wing moves further into the bay area,thereby creating an even greater overlap and barrier to the migration offines. When the blocks are fully rotated to the minimum allowableradius, the wing fills the bay area.

So, the invention as claimed hereinafter is essentially directed to asegmented retaining wall (SRW) block having a front wall, a rear walland two opposite side walls, wherein:

-   -   one of said side walls is rearwardly tapered so as to allow said        block to turn a radius when placed in adjacent position with        respect to another similar SRW block,    -   said rear wall is provided with a protruding wing that projects        laterally away from the tapered side wall;    -   said rear wall is also provided with a bay that extends inwardly        in the side wall that is opposite to the tapered side wall;    -   said wing and bay have front edges designed as congruent arcs;        and    -   said wing is sized and shaped so as to protrude into the bay of        an adjacent similar SRW block to create a barrier wherein said        adjacent SRW blocks are in straight, convex or concave        alignment.

The invention and its advantages will be better understood upon readingthe following non-restrictive description of a preferred embodimentthereof, made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a top plan view of a standard SRW block;

FIG. 1 b is a top plan view of a wall made of several SRW blocks asshown in FIG. 1 a;

FIG. 2 a is a top plan view of existing tapered SRW block;

FIG. 2 b is a top plan view of a wall made of several tapered SRW blocksas shown in FIG. 1 b;

FIG. 3 a is a top plan view of an existing SRW block with rear wingsthat can be knocked off;

FIG. 3 b is a top plan view of a wall made of SRW blocks as shown inFIG. 3 a, with their rear wings still present;

FIG. 4 b is a top plan view of a wall made of SRW blocks as shown inFIG. 3 b, with their rear wings knocked off;

FIG. 5 a is a top plan view similar to FIG. 2 b, with no gaps betweenthe rear sides of the blocks where the backfill material may migrate;

FIG. 5 b is a top plan view similar to FIG. 5 a but with the blocksplaced in radius larger than the minimum and backfill material inbetween;

FIG. 6 is a top plan view of a SRW block according to a preferredembodiment of the invention;

FIG. 7 is a top plan view of two SRW blocks as shown in FIG. 5 adjacentto each other, in a straight alignment;

FIG. 8 is a top plan view of two SRW blocks as shown in FIG. 5 in aconvex alignment;

FIG. 9 is a top plan view of two SRW blocks as shown in FIG. 5 in aconcave alignment; and

FIG. 10 is a view similar to the one of FIG. 7, but showing an enlargedview of the manufacturing and constructions tolerated.

In these drawings and the following description, the followingabbreviations or symbols correspond to the following:

Wface=Width of face of block

Point A=Rotation point of block on Side A

Side A=Left side of the block

Side B=Right side of the block

θ=Taper Angle on Side A of block

δ=Taper Angle on Side of bay B

Arc A=Arc length of protruding wing on Side A

Arc B=Arc length at bottom of bay area on Side B

Xs=Overlap length of arc A over arc B when blocks set in straightalignment

Xconvex=Overlap length of arc A over arc B when blocks set in minimumconvex curve (maximum overlap possible)

Xconcave=Overlap length of arc A over arc B when blocks set in minimumconcave curve (minimum overlap possible)

D=Front to back depth of block

Wd=Wing depth

Bd=Bay depth

t=Manufacturing and construction tolerances

Omin=Minimum overlap of wing into bay area in minimum concave alignment(worst case) to prevent infiltration of fines.

DETAILED DESCRIPTION OF THE INVENTION

The SRW block according to the preferred embodiment of the invention asshown in FIG. 6 is rectangular or square block having a left side (SideA) which differ from its right side (side B). The left side (Side A) ofthe block has an angle or tapered sidewall (angle=θ from the vertical).This angle represents the desired minimum convex radius the user wouldwant to achieve based on Equations 1 and 2 shown above.

In the illustrated preferred embodiment, Side A is tapered and Side B isstraight. However, Side A and Side B could also split, provided that thetotal taper angle (θ) remains between them.

In the illustrated preferred embodiment, the Side B has a straightsidewall for greater ease of explanation. From a manufacturing point ofview, it is also desirable to have a flat or straight sidewall on atleast one side of the block to move and package the material. Thetapered Side A allows the block to turn a convex radius in thetraditional way previously described. However, rather than continuingthe tapered sidewall right to the rear of the block, a wing protrudesout from the side of the block at the rear. The depth of the wing (Wd)is set to ensure that the wing piece be adequately strong to preventbreaking off during construction and shipping. The lower edge of thewing identified as arc A in FIG. 5, is formed as an arc. When two blocksare placed side by side, point A of one block is adjacent to point B ofthe other. As the block rotates its point A, the radius of the arc Aidentified in FIG. 5 as the wing radius (Rw) is as follow:

Rw=D−Wd   (Equation 3)

Indeed, when the center of rotation is point A, the radius is the blockdepth (D), minus the depth of the wing (Wd).

The wing (arc A) extends out past the imaginary vertical edge of Side A(viz. the side which is not tapered) at a distance noted as Xs. Thisdistance Xs is a function of the required minimum overlap in the worstcase scenario, which is, when the blocks are rotated outwards to form aconcave curve and the overlap is the minimum. This will be described inmore details hereinafter.

The straight sidewall (Side B) is designed on a congruent bay area inthe top right corner of the block that accepts the wing of side A. Thedepth of the bay area (Bd) is slightly larger than the depth of the wing(Wd) to allow construction and manufacturing tolerances.

Therefore, the value Bd−Wd is illustrative of the construction andmanufacturing tolerances.

The lower edge of the bay area on Side B (arc B) is designed as acongruent arc with arc A. The radius of the arc B is just slightly lessthan of arc A to allow movement of the wing into the bay area, given tomanufacturing and construction tolerances. Therefore, the radius of arcB, hereinafter called bay radius Rb, is equal to the wing radius (Rw)less the Manufacturing and Construction Tolerances (t).

Rb=Rw−t   (Equation 4)

The left sidewall of the bay area is designed to align (δ) with the leftside wall of the wing when the blocks are placed at the minimum convexrotation and the wing completely fills the bay area. The left sidewallof the wing is vertical when the block is placed in a straightalignment, so as it rotates into a convex curve, the vertical sidewallrotates about point A and is now angled. The left sidewall of the bayarea therefore must be set to the maximum angle the block is able torotate, which is θ.

Therefore:

θ=δ  (Equation 5)

The invention is designed to ensure that when the blocks are placed in astraight alignment, convex curve, or concave curve, an overlap of thewing and the bay area exists that is sufficient to prevent the migrationof backfill materials into the back of the blocks. FIG. 7 shows twoblocks placed adjacent to each other in a straight alignment. As can beseen, overlap is Xs. FIG. 8 shows two blocks placed adjacent to eachother in a convex alignment. This minimum convex radius is the best casescenario for providing a barrier to the infiltration of backfillmaterials. FIG. 9 shows two blocks placed adjacent to each other in aconcave alignment. This minimum concave radius is the worst casescenario for providing a barrier to the infiltration of the backfillmaterials.

The distance Xs which is the one of overlap in a straight alignment (seeFIG. 7) is determined by what the minimum offset can be in the worstcase scenario which is the distance Xconcave shown in FIG. 9.

Therefore, the protrusion of the wing beyond the imaginary verticalsidewall for Side A is determined as a function of the minimum radiusthat is required to be achieved by the block and the minimum overlap inthe concave alignment.

The total arc length of the arc A is therefore a function of the overlapin a minimum convex position plus the overlap in the minimum concaveposition plus the minimum overlap in the concave position. The equationfor the length of an arc is as follows (all angles being expressed indegrees):

Arc length (arc A)=(θ(PI)Rw)/90+Omin.   (Equation 6) and

Arc length (arc B)=arc A+t   (Equation 7)

Xs which is the portion of arc A that extends beyond the imaginaryvertical line along the sidewall A can then be expressed by thefollowing equation

Xs=(θ(PI)Rw)/180+Omin.   (Equation 8)

As may now be better understood, the arcs A and B formed at the bottomof the wing and bay area serve two purposes. First, they allow theseelements to rotate about point A while maintaining an exact distanceapart (depending on the manufacturing and construction tolerance) asthey follow an arc of consistent radius Rw (see FIG. 10). Secondly, thenature of the arc shape automatically creates an “uphill” configurationbetween the wing and the bay. In other words, if soil materials arebeing conveyed, either through gravity, water or compaction forces intothe bay area, they will encounter the bottom of the bay area and willnot be able to continue through the small space between the wing and thebay (left for construction and manufacturing tolerances) due to the factthat the direction of soil materials would have to be forced upward,against the direction of the applied conveyor forces. This “S” shapecreates a natural dam to the movement of material by its geometricconfiguration.

So, the configuration of segmental retaining wall blocks according tothe invention allows them to be set in a straight, concave, or convexalignment, while maintaining a mechanical barrier at the rear to theinfiltration of backfill soils.

1. A segmented retaining wall (SRW) block having a front wall, a rearwall and two opposite side walls, wherein: one of said side walls isrearwardly tapered so as to allow said block to turn a radius whenplaced in adjacent position with respect to another similar SRW block,said rear wall is provided with a protruding wing that projectslaterally away from the tapered side wall; said rear wall is alsoprovided with a bay that extends inwardly in the side wall that isopposite to the tapered side wall; said wing and bay have front edgesdesigned as congruent arcs; and said wing is sized and shaped so as toprotrude into the bay of an adjacent similar SRW block to create abarrier when said adjacent SRW blocks are in straight, convex or concavealignment.
 2. The SRW block of claim 1, wherein: the front edge of thewing has a wing radius; and the front edge of the bay has a bay radiuswhich is equal to the wing radius less the manufacturing andconstruction tolerances.
 3. The SRW block of claim 2, wherein the sidewall of the bay is designed to align with the corresponding side wall ofthe wing of an adjacent block when said blocks are placed at a minimumconvex rotation and the wing of said adjacent block completely fills thebay of the one block.